1. Field of the Invention
This invention generally relates to aircraft control systems, and in particular to pilot operable members of such control systems.
2. Description of the Prior Art
It is well recognized that aircraft control systems have become increasingly complex. This complexity is due to the requirement that aircraft, particularly tactical military aircraft, perform over a wide speed regime. Control system complexity has also increased due to a requirement for redundancy with so called "fly by wire systems" wherein there is no direct mechanical linkage between the pilot operated control member and the aircraft control surfaces.
Such control systems have included means for varying the force required to move the pilot operated member in response to the forces acting on the aircraft or the speed of the aircraft. Such force varying components and dampers have been connected in series between the pilot operated control member and the aircraft control surfaces so as to increase aircraft stability.
Additionally, high speed tactical aircraft tend to become unstable during certain speed regimes. In such cases, electronic stability augmentation systems are added to the aircraft control system so as to provide the requisite degree of inherent stability. Pilot induced oscillations, which tend to occur during certain speed regimes, are routinely compensated for by such stability augmentation systems. The electronic stability augmentation systems of the prior art are placed in series between the pilot operable member or control stick and the aircraft control surfaces.
It has long been recognized that movement of an aircraft may inadvertantly cause the pilot to move the control stick, thereby causing the aircraft to deviate, at least momentarily, from its desired flight path. A well known example of this "biodynamic feedthrough" occurs when an aircraft encounters turbulent air. The aircraft may be caused to pitch suddenly thereby causing the pilot to either pull or push the control stick. This biodynamic action causes further pitch excursions of the aircraft. Although this biodynamic feedthrough has been a problem to varying degrees, it has generally been handled by recognition of the problem by the aircraft pilot and the resulting appropriate pilot training. However, with advancing aircraft technology, such inadvertant deviations from the aircraft's desired flight path have become unacceptable.
For example, certain high technology, military tactical aircraft are now equipped with fuselage mounted deflectors which, when extended on one side of the aircraft, cause lateral movement of the aircraft in the opposite direction. Such lateral accelerations inadvertantly cause the pilot to laterally move the aircraft's control stick, thereby causing the aircraft to undesirably roll or rotate about its longitudinal axis.